(1) Field of the Invention
The present invention relates to an optical disc device and a laser beam power controlling method for the optical disc device, more particularly, which suppress erroneous data erasure owing to a servo-off in a multilayered disc.
(2) Description of the Related Art
Recently, an optical disc such as a DVD (Digital Versatile Disc) and a BD (Blu-ray Disc) has been developed to have a multilayered structure for higher storage capacity by increasing the number of recording layers. The BD of 3-layer or 4-layer type has been developed, and an optical disc device which allows the information data to be written to or read from the multilayered optical disc has also been under development.
As is well known, the information data written into the optical disc are read by irradiating laser beams from an optical pickup of the optical disc device so that the recording layer where the subject information data which have been written is focused, and by detecting the reflected light. On this occation, power of the laser beam is far lower than the power consumed for writing or erasing the information. When reading the information data, the laser beam power is severely controlled so as to prevent erroneous erasure of the information data caused by irradiation of high power laser beam by mistake.
Japanese Patent Application Laid-Open No. S61(1986)-142538 discloses the device for reducing quantity of laser beam incident on a recording medium upon operation other than recording, reproduction and erasing.
Japanese Patent Application Laid-Open No. S64(1988)-10431 discloses the device for reducing the laser beam power when the servo control is in the unlock state.
Japanese Patent Application Laid-Open No. 2001-176077 discloses the device for reducing the laser beam power to the one at reproduction in case of servo-control-off when recording the data in the multilayered optical disc.